Who is (was?) this DC Comics villain?

I first read a DC comics story with this villain back in the 80's. Some things I remember about the character:

• He is portrayed as the bringer of the end of the world


• His name had some connection to Armageddon or apocalypse or something like that


• He was said to have his base "at the end of time"


• In the story I read, he was fighting some time-traveling heroes